Featured Research

from universities, journals, and other organizations

The Ecology Of Fear: Wolves Gone, Western Ecosystems Suffer

Date:

December 15, 2004

Source:

Oregon State University

Summary:

Research about wolves that began in Yellowstone National Park has been replicated in an adjacent area, and a growing body of evidence leads scientists to conclude that this historic predator may have an ecological impact far more important than realized in the American West.

Share This

CORVALLIS, Ore. - Research about wolves that began in Yellowstone National Park has been replicated in an adjacent area, and a growing body of evidence leads scientists to conclude that this historic predator may have an ecological impact far more important than realized in the American West.

Related Articles

The near extinction of the gray wolf across most of the West in the past century now appears to have removed the natural element of "fear" from these ecosystems. It has triggered a cascade of ecological effects on everything from elk populations to beaver, birds, fish, and even stream systems - and helped lead directly to the collapsing health of aspen and some other tree species and vegetation.

Two recent studies by forestry scientists from Oregon State University, published in the journals BioScience and Forest Ecology and Management, outline a role for the gray wolf that is complex and rarely understood, but helps explain many major problems facing western streams, forests and wildlife.

"It would appear that the loss of a keystone predator, the gray wolf, across vast areas of the American West may have set the stage for previously unrecognized and unappreciated ecological changes in riparian and upland plant communities, and the functions they provide," the scientists concluded.

The studies were authored by William Ripple, a professor, and Robert Beschta, a professor emeritus, in the OSU College of Forestry.

In their research, the scientists explore a concept that has been called "the ecology of fear."

The ecological and historical significance of wolves is only partly due to the actual impact they have by preying on other animals, both large and small, the OSU researchers have found. Just as important is the fear that many larger animals have of wolves, and the resulting behavioral changes in elk and some other grazing animals.

"Prey species will alter their use of space and their foraging patterns according to the features of the terrain and how that affects the risk of predation," Ripple and Beschta noted in their study. "They forage or browse less intensively at high-risk sites."

Some of those sites, the researchers say, are streamsides rich in aspen, cottonwood, willow and other edible vegetation. When healthy and normal, such areas naturally grow large trees and other streamside vegetation that provides the basis for supporting beaver, other wildlife, fish populations, native bird communities, and stable channel banks.

The OSU scientists, in previous work, documented that the loss of aspen and cottonwood trees in Yellowstone National Park dated almost exactly to the extermination of the last wolf packs in the park in the mid-1920s.

The elk moved in, ate young trees before they could become established, and the entire riparian ecosystem began a slow demise that was only reversed recently - when wolves were re-introduced to the park.

In their newest work, the researchers have found exactly the same forces at work along the Gallatin River in southwestern Montana. Coincidental with the return of wolves to that area, there has been a dramatic recovery of willow populations along streams, and other possible factors such as changing climate conditions have been ruled out as a possible cause.

A modest recovery of willows may not seem that significant. But the OSU researchers say it has set the stage for ecological "spin-offs," including an increase in plant biomass, improved streambank stability, better floodplain functioning, reduced soil erosion, and better food web support for everything from beaver to river otter, fish, birds, amphibians, and insects. Biodiversity will increase and rising beaver populations will lead to even more changes, including sediment retention, wetland maintenance and nutrient cycling.

And the story, the OSU scientists say, appears to be much larger than just Yellowstone National Park or the mountainous regions around it, as demonstrated by a broad range of research.

One study suggested that the loss of wolves has allowed increases in deer populations across much of North America, which led to a browsing pressure on plants that was unprecedented. Predation effects involving wolves and elk were also found in aspen growth in Jasper National Park. In Grand Teton National Park, the local extinction of grizzly bears and wolves caused an increase in herbivory on willow by moose, and ultimately decreased the diversity of neotropical migrant birds.

The role of fear, while emphasizing the value of wolves, is not exclusive to them, the scientists said. Even the fear of human sport hunters has a role.

One study in Montana showed that elk adjusted their foraging behavior by browsing far from roads to avoid human contact and possible predation. And research in Colorado has found that aspen was far more heavily browsed, and used year-round by elk, where sport hunting was excluded.

Ultimately, however, the value of large predators needs to be reconsidered, the reports conclude. The body of evidence has become compelling, the OSU researchers say, that predation by top carnivores, especially wolves, may be pivotal to maintaining biodiversity in some ecosystems.

"The ranges of large carnivores are continuing to collapse around the world," the scientists note in their report. "In North America, the gray wolf and the grizzly bear have faced nearly complete extirpation in the lower 48 states, although populations of these carnivores have been increasing in recent years."

"Growing evidence points to the importance of conserving these animals because they have cascading effects on lower trophic levels."

A similar point, they said, was made by the great naturalist Aldo Leopold in 1949, who predicted this crisis.

"I have lived to see state after state extirpate its wolves," Leopold wrote 55 years ago. "I have seen every edible bush and seedling browsed, first to anemic desuetude, and then to death."

More From ScienceDaily

More Plants & Animals News

Featured Research

Mar. 3, 2015 — While studying a ground-nesting bird population near El Reno, Okla., a research team found that stress during a severe weather outbreak of May 31, 2013, had manifested itself into malformations in ... full story

Mar. 3, 2015 — The 3-D printing scene, a growing favorite of do-it-yourselfers, has spread to the study of plasma physics. With a series of experiments, researchers have found that 3-D printers can be an important ... full story

Mar. 3, 2015 — Most people consume more salt than they need and therefore have a higher risk of heart disease and stroke, which are the two leading causes of death worldwide. But a new study reveals that dietary ... full story

Mar. 3, 2015 — By examining the forces that the segments of mosquito legs generate against a water surface, researchers have unraveled the mechanical logic that allows the mosquitoes to walk on water, which may ... full story

Mar. 3, 2015 — Pediatric otolaryngologists and surgeons are concerned with parents getting the wrong message regarding the safety/desirability of letting babies and young children eat peanuts to prevent them from ... full story

Mar. 3, 2015 — Researchers have developed a new way of rapidly screening yeasts that could help produce more sustainable biofuels. The new technique could also be a boon in the search for new ways of deriving ... full story

Mar. 3, 2015 — Similar to humans and animals, plants possess an innate immune system that protects them from invading pathogens. Molecular structures that only occur in pathogens enable their recognition and ... full story

Mar. 3, 2015 — For almost a century, scientists have been puzzled by a process that is crucial to much of the life in Earth's oceans: Why does calcium carbonate, the tough material of seashells and corals, ... full story

Mar. 3, 2015 — To simulate chimp behavior, scientists created a computer model based on equations normally used to describe the movement of atoms and molecules in a confined space. An interdisciplinary research ... full story

Featured Videos

Rare Goblin Shark Found in Australia

AFP (Mar. 3, 2015) — A goblin shark, a rare sea creature described as an &apos;alien of the deep&apos; is found off Australia and delivered to the Australian Museum in Sydney. Duration: 01:25
Video provided by AFP

Zookeepers Copy Animal Poses In Hilarious Viral Photos

Buzz60 (Mar. 2, 2015) — Zookeepers at the Symbio Wildlife Park in Helensburgh, Australia decided to take some of their favorite animal photos and recreate them by posing just like the animals. Jen Markham (@jenmarkham) has the story.
Video provided by Buzz60

Related Stories

Nov. 16, 2012 — The number of wolves at Isle Royale National Park has dropped to its lowest ever. Should the wolves be let go locally extinct? Reintroduced? Wildlife ecologists and environmental ethicists weigh ... full story

Dec. 21, 2011 — On the 15th anniversary of the return of wolves to Yellowstone National Park, a quiet but profound rebirth of life and ecosystem health is emerging, scientists conclude in a new ... full story

Dec. 1, 2011 — A study of the wolves of Yellowstone National Park has improved predictions of how these animals will respond to environmental changes. The study, which is part of the Yellowstone Wolf Project, ... full story

Sep. 1, 2010 — Previous research has claimed that the reintroduction of wolves to Yellowstone National Park in 1995 is helping restore quaking aspen in risky areas where wolves prowl. But apparently elk hungry for ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.